This invention relates to automatic flow control valves. Valves of this type maintain a constant flow rate through a range of varying fluid pressures. A major drawback of the prior art has been that the structure of certain valve components would only accommodate a particular flow rate, and a multitude of valve components of different structural design were required in order to accommodate a range of desirable flow rates. Furthermore, once assembled and installed, no practical means is available to alter flow rates. The novel design and construction of an automatic flow control valve in accordance to the instant invention provide a plurality of flow rate requirements can be accommodated by a single valve construction.